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[Member] Denali Therapeutics Inc. Adjustment to Compensation: Adjustment to Compensation [Axis] Royalty percentage to be received Future Royalties Percentage To Be Received On Sale Of Product Future royalties percentage to be received on sale of product. 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Estimated future amortization of intangible assets Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments and Hedging Activities Disclosure [Abstract] Ionis, Sangamo, Denali and Sage Ionis, Sangamo, Denali and Sage [Member] Ionis, Sangamo, Denali and Sage Alcyone Therapeutics, Inc. Alcyone Therapeutics, Inc. [Member] Alcyone Therapeutics, Inc. 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No documentation exists for this element. -- Restructuring Restructuring and Related Activities Disclosure [Text Block] Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Goodwill, resulting from acquisition Goodwill, Acquired During Period SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] Ratio of total number of shares reserved under the plan Ratio Of Number Of Shares Reserved Under Plan Ratio of total number of shares reserved under the plan. 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Debt instrument, term Debt Instrument, Term (Gain) loss on strategic investments Increase (Decrease) in Equity Securities, FV-NI Effective Income Tax Rate Reconciliation [Table] Effective Income Tax Rate Reconciliation [Table] Property, plant and equipment, useful life Property, Plant and Equipment, Useful Life Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Subsequent Event Subsequent Event [Member] Other current assets(1) Business Combination, Recognized Asset Acquired, Other Asset, Current Milestone Payment, Sales-Based Milestone Payment, Sales-Based [Member] Milestone Payment, Sales-Based Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] BENEPALI BENEPALI [Member] BENEPALI [Member] PEO Total Compensation Amount PEO Total Compensation Amount Depreciation expense Depreciation Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Money market funds Money Market Funds [Member] Collaboration expense Collaboration Expenses Accrual Collaboration Expenses Accrual Liability derivative instruments Derivative Liability, Subject to Master Netting Arrangement, before Offset Equity Components [Axis] Equity Components [Axis] The Credit Facility The Credit Facility [Member] The Credit Facility Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Sublease income Sublease Income Non-current portion of notes payable Non-Current Portion Of Notes Payable And Term Loan [Member] Non-Current Portion Of Notes Payable And Term Loan Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Percentage of minimum investment return Percentage Of Minimum Investment Return Percentage of minimum investment return. 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Option exercise fee Contract Option Exercise Fee Contract Option Exercise Fee Euro Euro Member Countries, Euro Foreign currency cash flow hedge gain (loss) to be reclassified during next 12 months Foreign Currency Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months Unused borrowing capacity, amount Debt Instrument, Unused Borrowing Capacity, Amount LUNSUMIO LUNSUMIO [Member] LUNSUMIO Total current liabilities Liabilities, Current Operating Leased Assets [Line Items] Operating Leased Assets [Line Items] Inventory, other reserves and accruals Deferred Tax Assets, Inventory Due from joint venture Payables To Divestiture Of Interest In Joint Venture Payables To Divestiture Of Interest In Joint Venture Depreciation, amortization and other Deferred Tax Liabilities Depreciation Amortization Other Deferred tax liabilities depreciation amortization other. 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Expected receipts to co-fund development costs, noncurrent Collaborative Arrangement, Expected Development Cost Funds, Year Two Collaborative Arrangement, Expected Development Cost Funds, Year Two Furniture and fixtures Furniture and Fixtures, Gross Entity Small Business Entity Small Business Collaboration profit (loss) sharing Collaboration profit (loss) sharing Collaboration profit (loss) sharing Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] GAZYVA GAZYVA [Member] GAZYVA [Member] Net interest expense Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense Transition toll tax liabilities Deferred Tax Liabilities, Undistributed Foreign Earnings Preferred stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding Marketable equity securities: Debt Securities, Trading, and Equity Securities, FV-NI, Cost [Abstract] State Current State and Local Tax Expense (Benefit) Document Transition Report Document Transition Report Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration] Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration] Due after one year through five years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five Preferred stock, par value $0.001 per share Preferred Stock, Value, Outstanding Underlying Securities Award Underlying Securities Amount Future contingent payment for annual worldwide net sales that exceeding threshold, percentage Future Contingent Payment For Annual Worldwide Net Sales That Exceed $2.0 Billion Future Contingent Payment For Annual Worldwide Net Sales That Exceed $2.0 Billion Realized gains Debt Securities, Available-for-Sale, Realized Gain PSUs Settled in Cash Performance stock units settled in cash Performance Stock Units Settled in Cash [Member] Performance Stock Units Settled in Cash [Member] Equity Component [Domain] Equity Component [Domain] Document Period End Date Document Period End Date Payment Due At Second Anniversary Payment Due At Second Anniversary [Member] Payment Due At Second Anniversary Income Taxes Income Tax Disclosure [Text Block] U.K. UNITED KINGDOM Contingent consideration payments Payment for Contingent Consideration Liability, Financing Activities Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Percentage of earnings of the target number of units granted based on actual stock performance Maximum Target Number Of Market Stock Units Granted Based On Stock Performance In Percent Maximum target number of market stock units granted based on stock performance in percent. 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These payments include the reimbursement of our portion of third-party royalties that Elan pays on behalf of the collaboration, relating to sales outside of the U.S. These amounts are reflected in the collaboration profit sharing line in our consolidated statement of income. As sales of TYSABRI outside the U.S. increase, our collaboration profit sharing expense will increase. Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Sales trigger gross sales threshold Sales Trigger Gross Sales Threshold Sales trigger gross sales threshold. 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Summary of indebtedness Schedule of Debt [Table Text Block] Taxable intercompany dividend Effective Income Tax Rate Reconciliation, Equity in Earnings (Losses) of Unconsolidated Subsidiary, Amount Machinery and Equipment Machinery and Equipment [Member] Granted (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Tax Credits Effective Income Tax Rate Reconciliation, Tax Credit, Percent [Abstract] Other long-term liabilities Other Noncurrent Liabilities [Member] Collaborative Arrangement and Arrangement Other than Collaborative [Axis] Collaborative Arrangement and Arrangement Other than Collaborative [Axis] Restatement Determination Date: Restatement Determination Date [Axis] Issuance of common stock under stock award plan Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture Foreign Deferred Foreign Income Tax Expense (Benefit) Reduction of accounts receivable Accounts Receivable [Member] Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Restructuring and related costs Restructuring and Related Costs [Table Text Block] Income tax (benefit) expense: Income Tax Expense (Benefit), Continuing Operations [Abstract] Reduction of real estate footprint Reduction Of Real Estate Footprint Reduction Of Real Estate Footprint Other Proceeds from (Payment for) Other Financing Activity All Currencies [Domain] All Currencies [Domain] Effects of changes in tax laws or rates Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount Name Trading Arrangement, Individual Name Previously Reported Previously Reported [Member] Aggregate principal amount Debt Instrument, Face Amount Royalty revenue on sales of OCREVUS Royalty Attributed To OCREVUS [Member] Royalty Attributed To OCREVUS Subtotal: Biosimilars Biosimilars [Member] Biosimilars Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Global licensing collaboration, development and commercial milestone payments Global Licensing Collaboration Agreement, Research, Development, Regulatory and Commercial Milestone Payments Global Licensing Collaboration Agreement, Research, Development, Regulatory and Commercial Milestone Payments Share Repurchase Program [Axis] Share Repurchase Program [Axis] Preferred stock Preferred Stock [Member] Name Awards Close in Time to MNPI Disclosures, Individual Name Income before income tax (benefit) expense: Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest [Abstract] Beginning balance, unvested (in dollars per share) Ending balance, unvested (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Payment Payments for Restructuring Restructuring Type [Axis] Restructuring Type [Axis] Unrealized (losses) Unrealized Loss on Derivatives Unrealized Loss on Derivatives Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Other commitment Other Commitment ICFR Auditor Attestation Flag ICFR Auditor Attestation Flag Asset Acquisition [Line Items] Asset Acquisition [Line Items] 2017 Omnibus Equity Plan 2017 Omnibus Equity Plan [Member] 2017 Omnibus Equity Plan Cash equivalents, total Cash Equivalents, at Carrying Value Issuance of common stock under stock option and stock purchase plans (in shares) Stock Issued During Period, Shares, Treasury Stock Reissued Treasury stock, at cost; 23.8 million and 23.8 million shares, respectively Treasury Stock, Value Other clinical programs Other Clinical Programs [Member] Other Clinical Programs In-process research and development (omaveloxolone) In Process Research and Development [Member] After Second Threshold Date Percentage Of Co Promotion Operating Profits Greater Than First Fifty Million Option Two Sub Option Four Percentage Of Co Promotion Operating Profits Greater Than First Fifty Million Option Two Sub Option Four Term Loan 2023 Three-Year Tranche Term Loan 2023 Three-Year Tranche [Member] Term Loan 2023 Three-Year Tranche Defined Contribution Plan Disclosure [Line Items] Defined Contribution Plan Disclosure [Line Items] Overnight reverse repurchase agreements Repurchase Agreements [Member] Litigation Case [Axis] Litigation Case [Axis] Foreign Tax Jurisdiction Foreign Tax Jurisdiction [Member] Auditor Firm ID Auditor Firm ID Segments [Domain] Segments [Domain] Claims asserted Loss Contingency, Damages Sought, Value Government securities: Government Securities Current [Member] Government securities Current. Statement of Income Location, Balance [Axis] Statement of Income Location, Balance [Axis] Statement of Income Location, Balance [Axis] Foreign Income (Loss) from Continuing Operations before Income Taxes, Foreign Cash and Cash Equivalent [Table] Cash and Cash Equivalent [Table] Withholding tax Effective Income Tax Rate Reconciliation, Withholding Tax, Percent Effective Income Tax Rate Reconciliation, Withholding Tax, Percent Reportable Segment Reportable Segment [Member] Reportable Segment QALSODY QALSODY [Member] QALSODY Employee benefit plan obligations Defined Benefit Plan, Benefit Obligation 2017 Tax Act U.S. 2017 Tax Act [Member] U.S. 2017 Tax Act Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy and NAV [Domain] Genentech Roche Group Genentech Member Roche group Genentech. Statement of Financial Position Location, Balance [Domain] Statement of Financial Position Location, Balance [Domain] Inventory Increase (Decrease) in Inventories 5.200% Senior Notes due September 15, 2045 Senior Notes Five Point Two Percent Due Twenty Forty Five [Member] Senior Notes Five Point Two Percent Due Twenty Forty Five [Member] Potential future milestone payments commitment to third party approximately Potential Future Milestone Payments Commitment To Third Party Approximately Potential future milestone payments commitment to third party approximately. Other current assets: Derivative Asset [Abstract] Other credits Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items] Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items] Unrealized Gains (Losses) on Securities Available for Sale, Net of Tax Gains (losses) on securities available for sale AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-Sale, Parent [Member] Less: accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Earnings per Share Earnings Per Share, Policy [Policy Text Block] Measurement Period Adjustments, Accrued expense and other Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Accrued Expense And Other Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Accrued Expense And Other Revenue Recognition Revenue [Policy Text Block] Senior Notes Senior Notes [Member] Purchases of marketable securities Payments to Acquire Debt Securities, Available-for-Sale Defined Contribution Plan [Table] Defined Contribution Plan [Table] Accrued Expenses On Funding Commitment Related To Clinical Research Accrued Expenses On Funding Commitment Related To Clinical Research Accrued expenses on funding commitment related to clinical research. Estimated Fair Value Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Fair Value [Abstract] All Executive Categories All Executive Categories [Member] Components of deferred tax assets and liabilities Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Finished goods Inventory, Finished Goods, Net of Reserves Workforce Reduction Workforce Reduction [Member] Workforce Reduction Expected operating expense reduction Restructuring And Related Activities, Expected Operating Expense Reduction Restructuring And Related Activities, Expected Operating Expense Reduction Prepaid expense and other assets(1) Business Combination, Recognized Asset Acquired, Prepaid Expense and Other Asset, Current Title and Position [Axis] Title and Position [Axis] Proceeds from marketable securities, excluding strategic investments Realized Gain (Loss) on Investments [Table Text Block] Gene targets Research And Development, Gene Targets Research And Development, Gene Targets Commitments, contingencies and guarantees (Notes 22 and 23) Commitments and Contingencies Intangible assets: Business Combination, Recognized Asset Acquired, Identifiable Intangible Asset, Finite-Lived Business Combination [Axis] Business Combination [Axis] Comprehensive income (loss) Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Expected receipts to co-fund development costs, current Collaborative Arrangement, Expected Development Cost Funds, Year One Collaborative Arrangement, Expected Development Cost Funds, Year One Noncontrolling interests Noncontrolling Interest [Member] Revenues from anti-CD20 therapeutic programs Revenues from anti-CD20 therapeutic programs Revenues From Therapeutic Programs [Table Text Block] Revenues From Therapeutic Programs AVONEX AVONEX [Member] AVONEX LEQEMBI Collaboration LEQEMBI Collaboration [Member] LEQEMBI Collaboration Equity Method of Accounting Equity Method Investments [Policy Text Block] VUMERITY VUMERITY [Member] VUMERITY [Member] Ownership percentage Equity Method Investment, Ownership Percentage Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration] Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration] Contract manufacturing, royalty and other revenue Contract Manufacturing, Royalty And Other Revenue [Member] Contract Manufacturing, Royalty And Other Revenue PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Milestone Payment, Two Milestone Payment, Two [Member] Milestone Payment, Two Financial Instruments Cash, Cash Equivalent, and Marketable Security [Text Block] PLEGRIDY PLEGRIDY [Member] PLEGRIDY Revenue from Contract with Customer [Abstract] Revenue from Contract with Customer [Abstract] Hedging Designation [Axis] Hedging Designation [Axis] Scenario [Axis] Scenario [Axis] Deferred tax liability(1) Business Combination, Recognized Liability Assumed, Deferred Tax Liability Time-vested restricted stock units Time-Vested Restricted Stock Units (RSUs) RSUs Time Vested Restricted Stock Units [Member] Time vested restricted stock units. Reconciliation of beginning and ending amount of unrecognized tax benefits Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block] Unrealized gains (losses) on pension benefit obligation, net of tax Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax Net Gains/(Losses) Reclassified from AOCI into Operating Income (in millions) Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, before Tax Derivative Contract Type [Domain] Derivative Contract [Domain] Realized losses Debt Securities, Available-for-Sale, Realized Loss Collaborative Arrangement, Transaction with Party to Collaborative Arrangement Collaborative Arrangement, Transaction with Party to Collaborative Arrangement [Member] All Individuals All Individuals [Member] Long-term Debt, Type [Domain] Long-Term Debt, Type [Domain] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Purchases of property, plant and equipment Payments to Acquire Property, Plant, and Equipment 2023 Cost Saving Initiatives 2023 Cost Saving Initiatives [Member] 2023 Cost Saving Initiatives Name Forgone Recovery, Individual Name Unrealized gain (loss) on derivative instruments Net unrealized gains (losses) Unrealized Gain (Loss) on Derivatives Amounts receivable Accounts Receivable, From Collaborator Accounts Receivable, From Collaborator Share based payment arrangement, term Share-Based Compensation Arrangement by Share-Based Payment Award, Expiration Period Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested [Member] Reclassification out of Accumulated Other Comprehensive Income Reclassification out of Accumulated Other Comprehensive Income [Member] Payments/credits relating to sales in current year Payments Returns Applied Against Product Revenue Reserves Relating To Current Year Payments/ returns applied against product revenue reserves relating to current year. Due after five years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 5 Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 5 Amortized Cost Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Amortized Cost [Abstract] Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Schedule of Finite-Lived Intangible Assets [Table] Intangible Asset, Finite-Lived [Table] Geographical [Axis] Geographical [Axis] Other current liabilities: Derivative Liability [Abstract] Due from anti-CD20 therapeutic programs Increase (Decrease) in Other Operating Assets and Liabilities, Net Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Milestone Payment, Regulatory Or Commercial Milestone Payment, Regulatory Or Commercial [Member] Milestone Payment, Regulatory Or Commercial Development Milestones Development Milestones [Member] Development Milestones [Member] Foreign exchange (gains) losses, net Gain (Loss), Foreign Currency Transaction, before Tax Tax credits Deferred Tax Assets, Tax Credit Carryforwards SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] Forecast Forecast [Member] Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Title of 12(b) Security Title of 12(b) Security Statement [Table] Lessee, Lease, Description [Table] Ionis Pharmaceuticals Inc. Ionis Pharmaceuticals Inc. [Member] Ionis Pharmaceuticals Inc. GILTI, net of foreign tax credits Effective Income Tax Rate Reconciliation, GILTI, Percent Disposal Groups, Including Discontinued Operations [Table] Disposal Groups, Including Discontinued Operations [Table] Service, Other Service, Other [Member] Other comprehensive income (loss): Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Share of non-controling interest recognized Share Of Non-Controlling Interest Recognized Share Of Non-Controlling Interest Recognized Compensation related to share-based payments APIC, Share-Based Payment Arrangement, Option, Increase for Cost Recognition Net income per share: Earnings Per Share, Basic and Diluted [Abstract] (Deprecated 2022) Earnings Per Share [Abstract] 2030 Lessee, Operating Lease, Liability, to be Paid, Year Five Restructuring Plan [Axis] Restructuring Plan [Axis] Pillar Two taxes Effective Income Tax Rate Reconciliation, Pillar Two Taxes, Amount Effective Income Tax Rate Reconciliation, Pillar Two Taxes, Amount Other (income) expense, net Other (income) expense, net Nonoperating Income (Expense) Vanqua Bio, Inc. Vanqua Bio, Inc. [Member] Vanqua Bio, Inc. Due after five years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 5 Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 5 Tax credit carryforward, amount Tax Credit Carryforward, Amount Summary of common stock Summary Of Common Stock [Table Text Block] Summary of common stock. Share of non-controling interest recognized Share Of Non-Controling Interest Recognized Share Of Non-Controling Interest Recognized Exercised (in dollars per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Award Timing Disclosures [Line Items] Fair value of Reata equity compensation pre-acquisition services and related taxes Consideration transferred, equity compensation pre-acquisition services Business Combination, Consideration Transferred, Equity Compensation Pre-acquisition Services Business Combination, Consideration Transferred, Equity Compensation Pre-acquisition Services Components of inventory Schedule of Inventory, Current [Table Text Block] Gain (loss) on investments Gain (Loss) on Securities [Table Text Block] Regulatory Milestones Regulatory Milestones [Member] Regulatory Milestones [Member] Measurement Frequency [Domain] Measurement Frequency [Domain] Operating lease, renewal term Lessee, Operating Lease, Renewal Term Acquired in-process research and development Research and Development Asset Acquired in Transaction Other than Business Combination or Joint Venture Formation, Writeoff Equity Equity [Text Block] State Deferred State and Local Income Tax Expense (Benefit) Debt securities, available-for-sale, average maturity Debt Securities, Available-for-Sale, Average Maturity Debt Securities, Available-for-Sale, Average Maturity Net income attributable to Biogen Inc. Net income attributable to Biogen Inc. Net Income (Loss) Attributable to Parent Other Other Accrued Liabilities, Current Measurement input Intangible Asset, Measurement Input Intangible Asset, Measurement Input Returns Sales Returns and Allowances [Member] Reconciliation between the U.S. federal statutory tax rate and effective tax rate Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Vesting period Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period Other Effective Income Tax Rate Reconciliation, Other Adjustments, Percent Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Adoption Date Trading Arrangement Adoption Date 3.250% Senior Notes due February 15, 2051 Three Point Two Five Percent Senior Notes Due February Twenty Fifty One [Member] Three Point Two Five Percent Senior Notes Due February Twenty Fifty One Tax Credit Carryforward [Table] Tax Credit Carryforward [Table] Denominator: Denominator [Abstract] Denominator. Operating lease, contract term Lessee, Operating Lease, Term of Contract Customer [Axis] Customer [Axis] Selling, General and Administrative Expense Selling, General and Administrative Expenses, Policy [Policy Text Block] Line of Credit Line of Credit [Member] Accounting for Share-Based Compensation Compensation Related Costs, Policy [Policy Text Block] Retained earnings Retained Earnings (Accumulated Deficit) Strategic investment portfolio Strategic Investment Portfolio Strategic investment portfolio. Summary of share-based compensation expense associated with each of our share-based compensating programs Share-Based Payment Arrangement, Cost by Plan [Table Text Block] Range of durations of foreign currency forward contracts Derivative, Remaining Maturity Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member] Impairment of intangible assets Impairment of Intangible Assets, Indefinite-Lived (Excluding Goodwill) Class of Stock [Axis] Class of Stock [Axis] Unrealized Gains (Losses) on Cash Flow Hedges, Net of Tax Gains (losses) on cash flow hedges Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Other, net of foreign tax credits Effective Income Tax Rate Reconciliation, Cross-Border, Other, Amount Acquired in-process research and development, upfront and milestone expense Research And Development Expense (Acquired in Process Cost) Research And Development Expense (Acquired in Process Cost) Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table [Member] 2021 Senior Notes 2021 Senior Notes [Member] 2021 Senior Notes Retirement Plan Type [Axis] Retirement Plan Type [Axis] Facility Location [Axis] Facility Location [Axis] -- None. No documentation exists for this element. -- Commercial Milestones Commercial Milestones [Member] Commercial Milestones [Member] Other, net Other Nonoperating Income (Expense) Statement [Table] Statement [Table] Schedule of business acquisitions, by acquisition Business Combination [Table Text Block] Deferred income taxes Total deferred Deferred Income Tax Expense (Benefit) Adjustments to reconcile net income to net cash flow from operating activities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] Statute expirations Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations Cash flow from financing activities: Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Upfront payment for collaboration agreement Upfront Payment For Collaboration Agreement Upfront Payment For Collaboration Agreement Other foreign jurisdictions Foreign Tax Jurisdiction, Other [Member] Total assets acquired and liabilities assumed Business Combination, Recognized Asset Acquired to Liability Assumed, Excess (Less), and Goodwill Term of collaboration agreement Term Of Collaboration Agreement Term Of Collaboration Agreement All Adjustments to Compensation All Adjustments to Compensation [Member] Amendment Flag Amendment Flag Income tax effect Share-Based Payment Arrangement, Expense, Tax Benefit Sage Therapeutics Sage Therapeutics Inc. [Member] Sage Therapeutics Inc. Omnibus Plan number of shares authorized (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized Deferred Compensation Plan Other Postretirement Benefits Plan [Member] Collaborative arrangements, investments in counterparty Collaborative Arrangements, Investments In Counterparty Collaborative Arrangements, Investments In Counterparty City Therapeutics, Inc. City Therapeutics, Inc. [Member] City Therapeutics, Inc. Reduction in royalty rate Reduction In Royalty Rate Reduction In Royalty Rate Termination Date Trading Arrangement Termination Date Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Non-current portion: Long-Term Debt, Excluding Current Maturities [Abstract] Raw materials Inventory, Raw Materials, Net of Reserves Limit of gross sale of GAZYVA to be achieved in preceding 12 months under option one Threshold Of Gross Sales Of To Be Achieved In Preceding Twelve Consecutive Months Under Option One Threshold of gross sales of to be achieved in preceding twelve consecutive months under option one. Weighted average discount rate Operating Lease, Weighted Average Discount Rate, Percent Weighted-average number of common shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Basic Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table] Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table] Excess and obsolescence charges related to inventory Inventory Write-down Unrecognized tax benefit Unrecognized Tax Benefits that Would Impact Effective Tax Rate Amortization of acquired inventory step-up Amortization Of Inventory Step-Up Amortization Of Inventory Step-Up Basic and diluted earnings per share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Director Director [Member] Options exercisable (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Number Segment Reporting [Abstract] Segment Reporting [Abstract] Debt Disclosure [Abstract] Debt Disclosure [Abstract] Time-vested restricted stock units activity Time Vested Restricted Stock Units Activity [Table Text Block] Time Vested Restricted Stock Units Activity. Scenario [Domain] Scenario [Domain] Cost and expense: Costs and Expenses [Abstract] Income Tax Authority, Name [Axis] Income Tax Authority, Name [Axis] FAMPYRA(1) FAMPYRA [Member] FAMPYRA [Member] Restructuring and Related Activities [Abstract] Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Number of ophthalmolgy biosimilar products Number of Ophthalmology Biosimilar Products, Exclusive Rights Number of Ophthalmology Biosimilar Products, Exclusive Rights Purchased inventory valuation step-up and intangible assets Effective Income Tax Rate Reconciliation, Nondeductible Expense, Depreciation and Amortization, Percent Consolidated Entities [Axis] Consolidated Entities [Axis] Share-based Compensation Arrangement by Share-based Payment Award Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Litigation matter Effective Income Tax Rate Reconciliation, Litigation, Percent Effective Income Tax Rate Reconciliation, Litigation, Percent Less: Net (gains) losses realized on equity securities Equity Securities, FV-NI, Realized Gain (Loss) Percentage receivables of wholesale distributor accounted in consolidated receivables Percentage Receivables Of Wholesale Distributor Accounted In Consolidated Receivables Percentage receivables of wholesale distributor accounted in consolidated receivables. Granted (in shares) Stock options granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross Use of Estimates Use of Estimates, Policy [Policy Text Block] Aducanumab Aducanumab [Member] Aducanumab [Member] Construction in progress Construction in Progress, Gross Currency translation adjustments, net of tax Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Insider Trading Arrangements [Line Items] Forfeited (in dollars per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Debt Securities, Available-for-Sale, Amortized Cost [Abstract] Debt Securities, Available-for-Sale, Amortized Cost [Abstract] Total liabilities Liabilities Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Currency [Axis] Currency [Axis] 2024 ESPP 2024 ESPP [Member] 2024 ESPP Other (income) expense, net Other Nonoperating Income (Expense) [Member] Total marketable debt securities Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Amortized Cost Subtotal: Rare Disease Rare Disease Product Revenue [Member] Rare Disease Product Revenue Acquired In-process Research and Development, Upfront and Milestone Expense In Process Research and Development, Policy [Policy Text Block] Common stock, par value $0.0005 per share Common Stock, Value, Outstanding Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Additions based on tax positions related to the current period Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions Proceeds from sales and maturities of marketable securities Proceeds from maturities and sales Proceeds from Sale and Maturity of Debt Securities, Available-for-Sale Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Trademarks and trade names Trademarks and Trade Names [Member] Debt payable Business Combination, Recognized Liability Assumed, Long-Term Debt, Noncurrent Asset-backed Securities [Member] Asset-Backed Securities [Member] Counterparty Name [Axis] Counterparty Name [Axis] Deferred tax liabilities: Components of Deferred Tax Liabilities [Abstract] Marketable debt securities: Fair Value Debt Securities, Available-for-Sale Felzartamab And Izastobart/HIB210 Felzartamab And Izastobart/HIB210 [Member] Felzartamab And Izastobart/HIB210 Tax Credit Carryforward, Name [Domain] Tax Credit Carryforward, Name [Domain] Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Non-NEOs Non-NEOs [Member] Corporate debt securities Corporate Debt Securities [Member]